The present invention relates to apparatuses which has a function of allocating packets using such a technique as to logically combining a plurality of physical lines connected between apparatuses and to treat the physical lines as if they were a single line and packet allocation methods used for the apparatuses, and more particularly, relates to an apparatus which has a function of distributing or allocating packets in two steps of autonomously and beforehand avoiding a bandwidth overflow and effectively and suitably making the most of an excessive bandwidth in business fields of handling various sorts and types of traffics and also to a packet allocation method used for the apparatus.
Due to spread Internet use, improved CPU performances of personal computers, and appearance of multimedia personal computers; delivery of voice and video signals is widely employed in addition to transfer of text data in a packet transfer network. For the delivery of voice and video signals, it is required to suppress packet discard more severely than the text data. Thus it is necessary to avoid such packet discard.
A prior art packet transfer apparatus employing such a technique as to combining a plurality of physical ports into a logical port and treating the ports as the logical port, performs calculating operation on the basis of information (e.g., MAC address, IP address, port number, and VLAN identifier) in packets, selects output one of the physical ports based on the calculation result, and distributes the traffics to the selected output port.
However, there occurs a bias in the value of the calculation result based on the information within the packets. Thus when such packets are distributed as they are, the traffics are concentrated on a specific port and therefore efficient packet transfer cannot be achieved, since flow bandwidths in the physical ports in the local port are not averaged.
To avoid this, there is suggested a method of allocating nearly a uniform bandwidth to a plurality of physical ports in a logical port as a link aggregation (refer to JP-A-2006-5437). The link aggregation is a technique defined in IEEE802.1AX.
According to the method cited in JP-A-2006-5437, a data transfer apparatus as a traffic distribution control apparatus allocates traffics to a plurality of physical ports provided in a logical port as a link aggregation. To this end, the data transfer apparatus calculates a hash value for a received packet using a hash function on the basis of a transmission destination address and a transmission originator address of the received packet, and determines one of the physical ports as a destination. The data transfer apparatus includes a means for calculating a flow ratio between the plurality of physical ports, and a control means for changing allocation of the number of hash values to determine destination physical ports by feeding the calculated flow ratio back to bandwidth distribution or allocation ratios between the plurality of physical ports.
In the apparatus disclosed in JP-A-2006-5437, when a logic specified for determining the destination physical ports is not suitable, a bias probably occurs in the flow bandwidths allocated to the physical ports in the link aggregation. Even when such biased distribution or allocation is executed, it is not judged whether or not the determination is correct. At this time, a large quantity of packets flow. And when the packet quantity exceeds a total of flow bandwidths in the physical ports, this causes occurrence of a packet discard.
In order to solve the aforementioned problem, there are suggested a link aggregation circuit which can automatically select allocation logics according to a change in the property of a network and also a link aggregation allocation method used for the link aggregation circuit (refer to JP-A-2008-166881).
According to the method disclosed in JP-A-2008-166881, the link aggregation circuit using layer 2 for use of link aggregation has a plurality of ports for the link aggregation, a control means for automatically optimizing a MAC allocation logic, and a means for allocating flow-in packets to a plurality of ports based on the optimized MAC allocation logic.
However, the allocation logic optimizing method used in JP-A-2008-166881 is allocation based on a MAC address, and allocation based on packet-in information other than the MAC address is not carried out.
In the prior art packet transfer apparatus using such a technique as to combine a plurality of physical ports into a logical port and to handle the physical ports as the logical port, when flow bandwidths become unbalanced more or less or when a suitable packet distribution or allocation logic is not specified, a bias occurs in the flow bandwidths allocated to the physical ports. Under such a condition, when a large quantity of packets flows and the packet quantity exceeds a total of flow bandwidths of the physical ports, even presence of an excessive bandwidth in the other logically-combined physical ports will cause occurrence of a packet discard.
In recent years, an administrator or operator monitors flow bandwidths at all times, and when a bandwidth overflow is predicted, the operator manually adds a new line and changes output ports for packet flow. This may probably involve an error caused by the manual operation whenever the change is carried out.